During the development of the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) technical standards, there was much discussion for the flexibility to customize LTE to maximize performance in specific environments. Also, during discussions of the 3GPP LTE-Advanced (LTE-A) technical standards, many suggestions were made to manage interference level by using coordinated transmissions from different cells. It is well known that as cell size is decreased in an effort to improve spectral efficiency, interference increases.
In general, communications systems using beamforming make use of a number of transmit and/or receive antennas and signal processing to create fixed or adaptive transmit/receive beampatterns. The beampatterns may have a directional nature that may result in a performance improvement when compared with unidirectional transmit and/or receive antennas. The use of the beampatterns may yield a transmit/receive gain over communications systems using unidirectional transmit and/or receive antennas.
As such, beamforming has been promoted as a promising technique to increase cell coverage and to improve cell edge spectral efficiencies. However, a drawback of beamforming is the so called flashlight effect where the channel quality changes between mobile station (MS) measurement and base station (BS) transmission, due to the changes in the beampattern of the interfering neighbouring cells. Coordinated beamforming/switching has been suggested as a possible solution to this problem.